Alan T. Dorsey
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
A New Framework for Understanding Supersolidity in 4He
A New Framework for Understanding Supersolidity in 4He David S. Weiss Physics Department, The Pennsylvania State University, University Park, PA 16802, USA Recent experiments have detected 4He supersolidity, but the observed transition is rather unusual. In this paper, we describe a supersolid as a normal lattice suffused by a Bose gas. With this approach, we can explain the central aspects of the recent observations as well as previous experimental results. We conclude that detailed balance is violated in part of the 4He phase diagram, so that even in steady state contact with a thermal reservoir, the material is not in equilibrium. (submitted June 28, 2004) 67.80-s 1 The possibility that quantum solids exhibit supersolidity has been debated for 45 years1,2. The experimental search for the phenomenon culminated in the recent observations of Kim and Chan that the moment of inertia of solid 4He decreases at low temperature, both in porous media3 and in bulk4. These experiments strongly suggest a quantum phase transition to a supersolid state, especially because the effect is absent in solid 3He or when the annulus of their sample is blocked. However, the behavior of the transition is unexpected. It is gradual as a function of temperature, instead of sharp. The non-classical inertial effect starts to disappear at a very low critical velocity. When the supersolid is slightly doped with 3He, the reduction in inertia decreases, but the apparent transition temperature actually increases. In this paper, we present a new framework for understanding supersolidity in 4He. While consistent with earlier theoretical conceptions5,6, our framework allows for an interpretation of all available experimental data and for prediction of new phenomena. -
Density Fluctuations Across the Superfluid-Supersolid Phase Transition in a Dipolar Quantum Gas
PHYSICAL REVIEW X 11, 011037 (2021) Density Fluctuations across the Superfluid-Supersolid Phase Transition in a Dipolar Quantum Gas J. Hertkorn ,1,* J.-N. Schmidt,1,* F. Böttcher ,1 M. Guo,1 M. Schmidt,1 K. S. H. Ng,1 S. D. Graham,1 † H. P. Büchler,2 T. Langen ,1 M. Zwierlein,3 and T. Pfau1, 15. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany 2Institute for Theoretical Physics III and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany 3MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA (Received 15 October 2020; accepted 8 January 2021; published 23 February 2021) Phase transitions share the universal feature of enhanced fluctuations near the transition point. Here, we show that density fluctuations reveal how a Bose-Einstein condensate of dipolar atoms spontaneously breaks its translation symmetry and enters the supersolid state of matter—a phase that combines superfluidity with crystalline order. We report on the first direct in situ measurement of density fluctuations across the superfluid-supersolid phase transition. This measurement allows us to introduce a general and straightforward way to extract the static structure factor, estimate the spectrum of elementary excitations, and image the dominant fluctuation patterns. We observe a strong response in the static structure factor and infer a distinct roton minimum in the dispersion relation. Furthermore, we show that the characteristic fluctuations correspond to elementary excitations such as the roton modes, which are theoretically predicted to be dominant at the quantum critical point, and that the supersolid state supports both superfluid as well as crystal phonons. -
Sounds of a Supersolid A
NEWS & VIEWS RESEARCH hypothesis came from extensive population humans, implying possible mosquito exposure long-distance spread of insecticide-resistant time-series analysis from that earlier study5, to malaria parasites and the potential to spread mosquitoes, worsening an already dire situ- which showed beyond reasonable doubt that infection over great distances. ation, given the current spread of insecticide a mosquito vector species called Anopheles However, the authors failed to detect resistance in mosquito populations. This would coluzzii persists locally in the dry season in parasite infections in their aerially sampled be a matter of great concern because insecticides as-yet-undiscovered places. However, the malaria vectors, a result that they assert is to be are the best means of malaria control currently data were not consistent with this outcome for expected given the small sample size and the low available8. However, long-distance migration other malaria vectors in the study area — the parasite-infection rates typical of populations of could facilitate the desirable spread of mosqui- species Anopheles gambiae and Anopheles ara- malaria vectors. A problem with this argument toes for gene-based methods of malaria-vector biensis — leaving wind-powered long-distance is that the typical infection rates they mention control. One thing is certain, Huestis and col- migration as the only remaining possibility to are based on one specific mosquito body part leagues have permanently transformed our explain the data5. (salivary glands), rather than the unknown but understanding of African malaria vectors and Both modelling6 and genetic studies7 undoubtedly much higher infection rates that what it will take to conquer malaria. -
Defects in Novel Superfluids: Supersolid Helium and Cold Gases
DEFECTS IN NOVEL SUPERFLUIDS: SUPERSOLID HELIUM AND COLD GASES By KINJAL DASBISWAS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2012 ⃝c 2012 Kinjal Dasbiswas 2 To my parents, both physicians, who have always supported and nurtured my ambitions to be a physicist 3 ACKNOWLEDGMENTS I am grateful to my adviser, Professor Alan T. Dorsey, for the pivotal role he has played as a mentor in my PhD He introduced me to many topics in condensed matter physics, particularly the novel topic of supersolid helium. I have learned a number of techniques through working with him, but equally importantly, he has taught me to choose my problems carefully and to present my results in a coherent manner. I would like to thank Professors Peter J. Hirschfeld, Amlan Biswas, H.-P. Cheng and Susan B. Sinnott for useful discussions and for serving on my committee. I would also like to acknowledge Professors Y. -S. Lee and Pradeep Kumar for their valuable inputs about the supersolid problem, Professors D. L. Maslov, Richard Woodard, S. L. Shabanov, and K. A. Muttalib for their inspiring teaching, and the Max Planck Institute in Dresden for giving me the opportunity to attend a summer school on Bose-Einstein condensates. I am indebted to some of my graduate student colleagues for stimulating discussions and for ensuring a collegial environment in the department. I am grateful to K. Nichola and P. Marlin for their generous assistance with the administrative aspects of my graduate program. -
The Elastic Constants of a Nematic Liquid Crystal
The Elastic Constants of a Nematic Liquid Crystal Hans Gruler Gordon McKay Laboratory, Harvard University, Cambridge, Mass. 02138, U.S.A. (Z. Naturforsch. 30 a, 230-234 [1975] ; received November 4, 1974) The elastic constants of a nematic liquid and of a solid crystal were derived by comparing the Gibbs free energy with the elastic energy. The expressions for the elastic constants of the nematic and the solid crystal are isomorphic: k oc | D | /1. In the nematic phase | D | and I are the mean field energy and the molecular length. In the solid crystal, | D | and I correspond to the curvature of the potential and to the lattice constant, respectively. The measured nematic elastic constants show the predicted I dependence. 1. Introduction The mean field of the nematic phase was first derived by Maier and Saupe 3: The symmetry of a crystal determines the number D(0,P2) = -(A/Vn2)P2-P2±... (2) of non-vanishing elastic constants. In a nematic liquid crystal which is a uniaxial crystal, we find five 0 is the angle between the length axis of one mole- elastic constants but only three describe bulk pro- cule and the direction of the preferred axis (optical perties 2. Here we calculate the magnitude of these axis). P2 is the second Legendre polynomial and three elastic constants by determining the elastic P2 is one order parameter given by the distribution function f{0): energy density in two different ways. On the one hand the elastic energy density can be expressed by the elastic constants and the curvature of the optical p2 = Tf (@) Po sin e d e/tf (&) sin e d 0 . -
Superfluid Density in a Two-Dimensional Model of Supersolid
Eur. Phys. J. B 78, 439–447 (2010) DOI: 10.1140/epjb/e2010-10176-y THE EUROPEAN PHYSICAL JOURNAL B Regular Article Superfluid density in a two-dimensional model of supersolid N. Sep´ulveda1,2,C.Josserand2,a, and S. Rica3,4 1 Laboratoire de Physique Statistique, Ecole´ Normale Sup´erieure, UPMC Paris 06, Universit´eParisDiderot,CNRS, 24 rue Lhomond, 75005 Paris, France 2 Institut Jean Le Rond D’Alembert, UMR 7190 CNRS-UPMC, 4 place Jussieu, 75005 Paris, France 3 Facultad de Ingenier´ıa y Ciencias, Universidad Adolfo Ib´a˜nez, Avda. Diagonal las Torres 2640, Pe˜nalol´en, Santiago, Chile 4 INLN, CNRS-UNSA, 1361 route des Lucioles, 06560 Valbonne, France Received 28 February 2010 / Received in final form 27 October 2010 Published online 6 December 2010 – c EDP Sciences, Societ`a Italiana di Fisica, Springer-Verlag 2010 Abstract. We study in 2-dimensions the superfluid density of periodically modulated states in the frame- work of the mean-field Gross-Pitaevskiˇı model of a quantum solid. We obtain a full agreement for the su- perfluid fraction between a semi-theoretical approach and direct numerical simulations. As in 1-dimension, the superfluid density decreases exponentially with the amplitude of the particle interaction. We discuss the case when defects are present in this modulated structure. In the case of isolated defects (e.g. dislocations) the superfluid density only shows small changes. Finally, we report an increase of the superfluid fraction up to 50% in the case of extended macroscopical defects. We show also that this excess of superfluid fraction depends on the length of the complex network of grain boundaries in the system. -
Liquid Crystals
www.scifun.org LIQUID CRYSTALS To those who know that substances can exist in three states, solid, liquid, and gas, the term “liquid crystal” may be puzzling. How can a liquid be crystalline? However, “liquid crystal” is an accurate description of both the observed state transitions of many substances and the arrangement of molecules in some states of these substances. Many substances can exist in more than one state. For example, water can exist as a solid (ice), liquid, or gas (water vapor). The state of water depends on its temperature. Below 0̊C, water is a solid. As the temperature rises above 0̊C, ice melts to liquid water. When the temperature rises above 100̊C, liquid water vaporizes completely. Some substances can exist in states other than solid, liquid, and vapor. For example, cholesterol myristate (a derivative of cholesterol) is a crystalline solid below 71̊C. When the solid is warmed to 71̊C, it turns into a cloudy liquid. When the cloudy liquid is heated to 86̊C, it becomes a clear liquid. Cholesterol myristate changes from the solid state to an intermediate state (cloudy liquid) at 71̊C, and from the intermediate state to the liquid state at 86̊C. Because the intermediate state exits between the crystalline solid state and the liquid state, it has been called the liquid crystal state. Figure 1. Arrangement of Figure 2. Arrangement of Figure 3. Arrangement of molecules in a solid crystal. molecules in a liquid. molecules in a liquid crystal. “Liquid crystal” also accurately describes the arrangement of molecules in this state. In the crystalline solid state, as represented in Figure 1, the arrangement of molecules is regular, with a regularly repeating pattern in all directions. -
Liquid Crystals - the 'Fourth' Phase of Matter
GENERAL I ARTICLE Liquid Crystals - The 'Fourth' Phase of Matter Shruti Mohanty The remarkable physical properties of liquid crystals have been exploited for many uses in the electronics industry_ This article summarizes the physics of these beautiful and I • complex states of matter and explains the working of a liquid crystal display. Shruti Mohanty has worked What are Liquid Crystals? on 'thin film physics of free standing banana liquid The term 'liquid crystal' is both intriguing and confusing; while crystal films' as a summer it appears self-contradictory, the designation really is an attempt student at RRI, Bangalore. to describe a particular state of matter of great importance She is currently pursuing her PhD in Applied Physics today, both scientifically and technologically. TJ!e[:w:odynamic at Yale University, USA. phases of condensed matter with a degree of order intermediate Her work is on supercon between that of the crystalline solid and the simple liquid are ductivity, particularly on called liquid crystals or mesophases. They occutliS Stable phases superconducting tunnel 'junctions and their for many compounds; in fact one out of approximately two applications. hundred synthesized organic compounds is a liquid crystalline material. The typical liquid crystal is highly ani'sotropic - in some cases simply an anisotropic liquid, in other cases solid-like in some directions. Liquid-crystal physics, although a field in itself, is often in cluded in the larger area called 'soft matter', including polymers, colloids, and surfactant solutions, all of which are highly de formable materials. This property leads to many unique and exciting phenomena not seen in ordinary condensed phases, and possibilities of novel technological applications. -
Strange Elasticity of Liquid Crystal Rubber: Critical Phase
Strange elasticity of liquid-crystal rubber University of Colorado Boulder $ NSF-MRSEC, Materials Theory, Packard Foundation UMass, April 2011 Outline • Diversity of phases in nature! • Liquid-crystals! • Rubber! • Liquid-crystal elastomers! • Phenomenology! • Theory (with Xing, Lubensky, Mukhopadhyay)! • Challenges and future directions! “White lies” about phases of condensed matter T P States of condensed matter in nature • magnets, superconductors, superfluids, liquid crystals, rubber, ! colloids, glasses, conductors, insulators,… ! Reinitzer 1886 (nematic, Blue phase) Liquid Crystals … T crystal … smectic-C smectic-A nematic isotropic cholesteric smectic layer vortex lines pitch fluctuations Reinitzer 1886 (nematic, Blue phase) Liquid Crystals … T crystal … smectic-C smectic-A nematic isotropic cholesteric smectic layer vortex lines pitch fluctuations • Rich basic physics – critical phenomena, hydrodynamics, coarsening, topological defects, `toy` cosmology,… • Important applications – displays, switches, actuators, electronic ink, artificial muscle,… N. Clark Liquid-crystal beauty “Liquid crystals are beautiful and mysterious; I am fond of them for both reasons.” – P.-G. De Gennes! Chiral liquid crystals: cholesterics cholesteric pitch • color selective Bragg reflection from cholesteric planes • temperature tunable pitch à wavelength Bio-polymer liquid crystals: DNA M. Nakata, N. Clark, et al Nonconventional liquid crystals • electron liquid in semiconductors under strong B field! 4 5 4 5 4 5 4 half-filled high Landau levels! ν=4+½ • -
Supersolid State of Matter Nikolai Prokof 'Ev University of Massachusetts - Amherst, [email protected]
University of Massachusetts Amherst ScholarWorks@UMass Amherst Physics Department Faculty Publication Series Physics 2005 Supersolid State of Matter Nikolai Prokof 'ev University of Massachusetts - Amherst, [email protected] Boris Svistunov University of Massachusetts - Amherst, [email protected] Follow this and additional works at: https://scholarworks.umass.edu/physics_faculty_pubs Part of the Physical Sciences and Mathematics Commons Recommended Citation Prokof'ev, Nikolai and Svistunov, Boris, "Supersolid State of Matter" (2005). Physics Review Letters. 1175. Retrieved from https://scholarworks.umass.edu/physics_faculty_pubs/1175 This Article is brought to you for free and open access by the Physics at ScholarWorks@UMass Amherst. It has been accepted for inclusion in Physics Department Faculty Publication Series by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. On the Supersolid State of Matter Nikolay Prokof’ev and Boris Svistunov Department of Physics, University of Massachusetts, Amherst, MA 01003 and Russian Research Center “Kurchatov Institute”, 123182 Moscow We prove that the necessary condition for a solid to be also a superfluid is to have zero-point vacancies, or interstitial atoms, or both, as an integral part of the ground state. As a consequence, superfluidity is not possible in commensurate solids which break continuous translation symmetry. We discuss recent experiment by Kim and Chan [Nature, 427, 225 (2004)] in the context of this theorem, question its bulk supersolid interpretation, and offer an alternative explanation in terms of superfluid helium interfaces. PACS numbers: 67.40.-w, 67.80.-s, 05.30.-d Recent discovery by Kim and Chan [1, 2] that solid 4He theorem. -
Introduction to Liquid Crystals
Introduction to liquid crystals Denis Andrienko International Max Planck Research School Modelling of soft matter 11-15 September 2006, Bad Marienberg September 14, 2006 Contents 1 What is a liquid crystal 2 1.1 Nematics . 3 1.2 Cholesterics . 4 1.3 Smectics.............................................. 5 1.4 Columnar phases . 6 1.5 Lyotropic liquid crystals . 7 2 Long- and short-range ordering 7 2.1 Order tensor . 7 2.2 Director . 9 3 Phenomenological descriptions 10 3.1 Landau-de Gennes free energy . 10 3.2 Frank-Oseen free energy . 11 4 Nematic-isotropic phase transition 14 4.1 Landau theory . 14 4.2 Maier-Saupe theory . 15 4.3 Onsager theory . 17 5 Response to external fields 18 5.1 Frederiks transition in nematics . 18 6 Optical properties 20 6.1 Nematics . 20 6.2 Cholesterics . 22 7 Defects 23 8 Computer simulation of liquid crystals 24 9 Applications 27 1 Literature Many excellent books/reviews have been published covering various aspects of liquid crystals. Among them: 1. The bible on liqud crystals: P. G. de Gennes and J. Prost “The Physics of Liquid Crystals”, Ref. [1]. 2. Excellent review of basic properties (many topics below are taken from this review): M. J. Stephen, J. P. Straley “Physics of liquid crystals”, Ref. [2]. 3. Symmetries, hydrodynamics, theory: P. M. Chaikin and T. C. Lubensky “Principles of Condensed Matter Physics”, Ref. [3]. 4. Defects: O. D. Lavrentovich and M. Kleman, “Defects and Topology of Cholesteric Liquid Crys- tals”, Ref. [4]; Oleg Lavrentovich “Defects in Liquid Crystals: Computer Simulations, Theory and Experiments”, Ref. -
Quantum Hydrodynamics for Supersolid Crystals and Quasicrystals
Quantum hydrodynamics for supersolid crystals and quasicrystals The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Heinonen, Vili et al. "Quantum hydrodynamics for supersolid crystals and quasicrystals." Physical Review A 99, 6 (June 2019): 063621 © 2019 American Physical Society As Published http://dx.doi.org/10.1103/physreva.99.063621 Publisher American Physical Society (APS) Version Final published version Citable link https://hdl.handle.net/1721.1/123298 Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. PHYSICAL REVIEW A 99, 063621 (2019) Quantum hydrodynamics for supersolid crystals and quasicrystals Vili Heinonen,1,* Keaton J. Burns,2 and Jörn Dunkel1,† 1Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA 2Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA (Received 3 August 2018; published 24 June 2019) Supersolids are theoretically predicted quantum states that break the continuous rotational and translational symmetries of liquids while preserving superfluid transport properties. Over the last decade, much progress has been made in understanding and characterizing supersolid phases through numerical simulations for specific interaction potentials. The formulation of an analytically tractable framework for generic interactions still poses theoretical challenges. By going beyond the usually considered quadratic truncations, we derive a systematic higher-order generalization of the Gross-Pitaevskii mean-field model in conceptual similarity with the Swift- Hohenberg theory of pattern formation.